Injection control device

ABSTRACT

An injection control device includes: an arithmetic unit that obtains a valve-closing time for stopping injection of fuel from a fuel injection valve based on a degree of variation in a time change of a voltage generated when the fuel injection valve is driven based on a required injection amount; an injection amount change unit that increases or decreases the required injection amount; and a learning unit that repeats injection control of the fuel to learn the valve-closing time obtained by the arithmetic unit.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of priority from JapanesePatent Application No. 2020-154614 filed on Sep. 15, 2020. The entiredisclosure of the above application is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an injection control device forcontrolling the opening and closing of a fuel injection valve.

BACKGROUND

The injection control device opens and closes a fuel injection valve toinject fuel into an internal combustion engine. A general fuel injectionvalve separates a valve element from an injection valve body having aninjection hole for fuel and attaches the valve element to the injectionvalve body, thereby opening and closing the injection hole. The fuelinjection valve incorporates a solenoid coil and electrically drives thesolenoid coil to control the position of the valve element.

In the injection control device, when the energization of the solenoidcoil is started or stopped, the valve element operates behind theenergization start time or energization stop time. Thus, in order toaccurately adjust the injection amount, it is necessary to adjust theenergization time in consideration of the delay times. The delay timevaries due to the use environment, aging deterioration, and individualvariation of the fuel injection valve, variation in process, voltage,and temperature (PVT) of a component parameter such as a drive circuitfor driving the fuel injection valve, and the like, and hence thevalve-opening time and the valve-closing time of the valve element varyon the basis of various environmental changes described above.Therefore, a technique for estimating these timings has been provided.

When the valve-closing time is detected by using the differentialmethod, correction is required so that a twice differential valuecoincides with the valve-closing time. Hence it is preferable todirectly detect the valve-closing time by detecting the degree ofvariation such as a dispersion value. In a comparative technique, atleast one of a voltage value or a current value of an electromagneticcoil is acquired as a sample value at a predetermined time intervalduring a sampling period set with a predetermined reference timing as areference, and the start time or the completion time of the valveopening or closing is estimated on the basis of the calculation of thedegree of variation in the sample value.

SUMMARY

An injection control device includes: an arithmetic unit that obtains avalve-closing time for stopping injection of fuel from a fuel injectionvalve based on a degree of variation in a time change of a voltagegenerated when the fuel injection valve is driven based on a requiredinjection amount; an injection amount change unit that increases ordecreases the required injection amount; and a learning unit thatrepeats injection control of the fuel to learn the valve-closing timeobtained by the arithmetic unit.

BRIEF DESCRIPTION OF DRAWINGS

The above and other features and advantages of the present disclosurewill be more clearly understood from the following detailed descriptionwith reference to the accompanying drawings. In the accompanyingdrawings,

FIG. 1 is an electrical configuration of an injection control deviceaccording to an embodiment;

FIG. 2 is a longitudinal sectional side view schematically illustratingan internal structure of a fuel injection valve;

FIG. 3 is an electrical configuration of a drive circuit;

FIG. 4 is a functional configuration diagram of a microcomputer and acontrol IC;

FIG. 5 is a diagram schematically illustrating a voltage change thatoccurs in a solenoid coil after de-energization;

FIG. 6 is a flowchart schematically illustrating a flow for obtaining aregion in which the degree of variation is detectable;

FIG. 7 is a timing chart (first part) schematically illustrating a flowfor obtaining a region in which the degree of variation is detectable;

FIG. 8 is a timing chart (second part) schematically illustrating a flowfor obtaining a region in which the degree of variation is detectable;and

FIG. 9 is a timing chart schematically illustrating a flow for obtaininga region in which the degree of variation is detectable.

DETAILED DESCRIPTION

For example, in the case of minute injection, it is difficult for theinjection control device to detect the degree of variation in the samplevalue. When the degree of variation cannot be detected, thevalve-closing time cannot be detected and learned, and the injectionamount cannot be highly accurately corrected on the basis of the learnedvalve-closing time.

One example of the present disclosure provides an injection controldevice capable of reliably learning a valve-closing time.

According to one example embodiment, an injection control device drivesa fuel injection valve to control the injection of fuel to an internalcombustion engine. An arithmetic unit obtains a valve-closing time forstopping the injection of the fuel from the fuel injection valve basedon a degree of variation in a time change of a voltage generated whenthe fuel injection valve is driven based on a required injection amount.An injection amount change unit increases or decreases the requiredinjection amount. A learning unit repeats injection control of the fuelbased on the required injection amount that is increased or decreased bythe injection amount change unit, to learn the valve-closing timeobtained by the arithmetic unit. As a result, it is possible to obtainthe region of the required injection amount with which the degree ofvariation can be detected, calculate a range in which a valve-closingtime can be learned, and learn the valve-closing time with highreliability.

Hereinafter, an embodiment of an injection control device will bedescribed with reference to the drawings. As illustrated in FIG. 1, anelectronic control unit 1 (ECU) is configured as an injection controldevice for driving a solenoid type fuel injection valve 2 that directlyinjects and supplies fuel to an internal combustion engine mounted on avehicle such as an automobile, for example. The fuel injection valve 2is also referred to as an injector. In the following, a form in whichthe present disclosure is applied to an electronic control unit 1 forcontrolling a gasoline engine will be described, but the presentdisclosure may also be applied to an electronic control unit forcontrolling a diesel engine. The fuel injection valve 2 for fourcylinders is illustrated in FIG. 1, but the present disclosure can alsobe applied to a three-cylinder engine, a six-cylinder engine, and aneight-cylinder engine.

As illustrated in FIG. 2, the fuel injection valve 2 includes a solenoidcoil 4, a valve element 5, a fixed core 6, and a movable core 7 in abody 3. The valve element 5 has a cylindrical shape as a whole and aconical shape on the tip side and is accommodated inside the body 3 soas to be movable forward in the axial direction. The body 3 is providedwith a fuel injection hole 3 a at the tip side of the valve element 5.

The fixed core 6 is fixed to the body 3. The fixed core 6 is formed ofmagnetic material in a cylindrical shape, and a fuel passage is formedinside the cylinder of the fixed core 6. The movable core 7 is providedinside the body 3 and around the valve element 5. The movable core 7 isformed in a disk shape using metallic magnetic material and is providedon the side of the injection hole 3 a relative to the fixed core 6.

The movable core 7 is positioned inside the solenoid coil 4 and disposedso as to be movable forward in the axial direction. When the solenoidcoil 4 is not energized, the movable core 7 is disposed facing the fixedcore 6 so as to have a predetermined gap with the fixed core 6. Athrough hole is formed inside the movable core 7, the valve element 5 isinserted and disposed in the through hole, and the movable core 7 is incontact with a locking portion 5 a of the valve element 5. The lockingportion 5 a is fixed to the valve element 5 and is formed between themovable core 7 and the fixed core 6, and when the movable core 7operates toward the fixed core 6, the valve element 5 is interlocked viathe locking portion 5 a.

A first spring 8 is wound inside the fixed core 6 and around the valveelement 5. The first spring 8 is disposed to apply an elastic force tothe valve element 5 on the side of the injection hole 3 a. A secondspring 9 is positioned on the side of the injection hole 3 a of themovable core 7 and fixed to the body 3. When the solenoid coil 4 is notenergized, the second spring 9 holds the movable core 7 at the initialposition.

When the energization of the solenoid coil 4 is started, the movablecore 7 is attracted to the fixed core 6 against the elastic force of thesecond spring 9. When the movable core 7 operates, the valve element 5operates in the axial direction via the locking portion 5 a. Then, themovable core 7 comes into contact with the fixed core 6. Even when themovable core 7 is in contact with the fixed core 6, the locking portion5 a of the valve element 5 operates in the axial direction away from themovable core 7 and, whereby the valve element 5 is moved relative to themovable core 7. In the fuel injection valve 2, by the operation of thevalve element 5, the tip side of the valve element 5 opens the injectionhole 3 a of the body 3 to inject fuel into the combustion chamber of theinternal combustion engine

When the energization of the solenoid coil 4 is stopped, the movablecore 7 is returned to the initial position by the elastic force of thefirst spring 8 and the second spring 9. Thus, the tip side of the valveelement 5 blocks the injection hole 3 a of the body 3 to stop the fuelinjection, and the fuel injection valve 2 is closed.

Next, an electrical configuration of the electronic control unit 1 willbe described. As illustrated in FIG. 1, the electronic control unit 1has an electrical configuration as a booster circuit 13, a microcomputer14, a control integrated circuit (IC) 15, and a drive circuit 16.

The microcomputer 14 includes one or more cores 14 a, a memory 14 b suchas read-only memory (ROM) and random-access memory (RAM), and aperipheral circuit 14 c such as an analog-to-digital (A/D) converter,performs various kinds of control in parallel on the basis ofapplication programs stored in the memory 14 b and sensor signals Sacquired from various sensors 18, and drives the fuel injection valve 2with a current to control the injection of fuel to the combustionchamber of the internal combustion engine.

For example, the sensor 18 for a gasoline engine includes a crank anglesensor that outputs a pulse signal each time a crankshaft rotates at apredetermined angle, a fuel pressure sensor that detects fuel pressureduring fuel injection, a throttle opening sensor that detects a throttleopening, an intake air temperature sensor that detects the temperatureof intake air, a water temperature sensor that detects cooling watertemperature, an intake air amount sensor 18 a that detects the amount ofintake air, an A/F sensor 18 b that detects an air-fuel ratio, that isan A/F value, of the exhaust of the internal combustion engine, and someother sensor. FIG. 1 schematically illustrates the sensor 18.

The microcomputer 14 calculates the rotational speed of the internalcombustion engine by using a pulse signal of the crank angle sensor andacquires a throttle opening from a throttle opening signal. Themicrocomputer 14 calculates a target torque required for the internalcombustion engine on the basis of the throttle opening, hydraulicpressure, and the A/F value and calculates a target required injectionamount on the basis of the target torque.

The microcomputer 14 calculates an energization command time Ti on thebasis of the target required injection amount and the fuel pressuredetected by the fuel pressure sensor and generates an injection commandsignal TQ. The microcomputer 14 calculates an injection startinstruction time for each cylinder #1 to #4 on the basis of the sensorsignals S input from the various sensors 18 and outputs the injectioncommand signal TQ to the control IC 15 at the injection startinstruction time.

The control IC 15 is, for example, an integrated circuit device using anapplication-specific integrated circuit (ASIC) and, although notillustrated, the control IC 15 includes a control body such as a logiccircuit and a central processing unit (CPU), a memory 15 e such as RAM,ROM, an erasable programmable read-only memory (EEPROM), comparatorequipment using a comparator, and the like, for example, and isconfigured to perform various kinds of control on the basis of hardwareand software. The control IC 15 has functions as a boosting control unit15 a, an energization control unit 15 b, a current monitoring unit 15 c,and a voltage monitor unit 15 d. In the drawings, the boosting controlunit 15 a may be also referred to as BOOSTING CONT, the energizationcontrol unit 15 b may be also referred to as ENERGIZATION CONT, thecurrent monitoring unit 15 c may be also referred to as CURRENT CONT,and the voltage monitor unit 15 d may be also referred to as VOLTAGEMONITORING.

The booster circuit 13 includes a boosting type DC-to-DC converter. Thebooster circuit 13 receives input of a battery voltage VB to performboost operation and charges a charge capacitor 13 a serving as a chargeunit with a boosting voltage Vboost.

The boosting control unit 15 a controls the boosting of the batteryvoltage VB input into the booster circuit 13. The boosting control unit15 a detects the boosting voltage Vboost of the charge capacitor 13 a ofthe booster circuit 13, performs charge with the detected boostingvoltage Vboost to a fully charged voltage, and supplies the detectedboosting voltage Vboost to the drive circuit 16.

The drive circuit 16 receives the input of the battery voltage VB andthe boosting voltage Vboost and operates. The drive circuit 16 applies avoltage to the solenoid coil 4 on the basis of the energization controlof the energization control unit 15 b of the control IC 15 to directlyinject fuel from the fuel injection valve 2 to each cylinder #1 to #4.As illustrated in FIG. 3, the drive circuit 16 includes upstreamcircuits 16 a, 16 b connected upstream of the solenoid coil 4, adownstream circuit 16 c connected downstream of the solenoid coil 4, anda current detection unit 16 e. In the drawings, the current detectionunit 16 e may be also referred to as CURRENT DETECT.

The upstream side of the solenoid coils 4 for two cylinders is commonlyconnected at a node N1, and the upstream side of the solenoid coils 4for the other two cylinders is commonly connected at a node N2. Theupstream circuits 16 a, 16 b are connected to the nodes N1 and N2,respectively, so as to be energized and are connected so that a voltagecan be applied to the fuel injection valves 2 for two cylinders,respectively. The upstream circuits 16 a, 16 b have the sameconfiguration. Here, the configuration of the upstream circuit 16 a willbe described, and the configuration of the upstream circuit 16 b will beomitted.

A drain-source of the MOSFET_M2 is connected between a supply node ofthe boosting voltage Vboost and the node N1. A boost circuit BT isconnected to the source of the MOSFET_M2, and the supply capacity of theboosting voltage Vboost can be improved by the boost circuit BT. Adrain-source of a MOSFET_M3 and an anode-cathode of a diode D2 areconnected between a supply node of the battery voltage VB and the nodeN1. The diode D2 is provided to prevent the reverse flow of the boostingvoltage Vboost.

Thus, when the energization control unit 15 b turns on the MOSFET_M2,the boosting voltage Vboost can be applied to the solenoid coil 4 of thefuel injection valve 2 for two cylinders through the node N1. When theenergization control unit 15 b turns on the MOSFET_M3, the batteryvoltage VB can be applied to the solenoid coil 4 of the fuel injectionvalve 2 for two cylinders through the node N1. A reflux diode D3 isconnected between the ground and the node N1.

On the other hand, the downstream circuit 6 c is a cylinder selectionswitch for selecting the cylinders #1 to #4 to be injected with fuel andincludes a MOSFET_M4. The energization control unit 15 b can energize adesired solenoid coil 4 by turning on one or two MOSFETs_M4 at a desiredtiming. A regeneration circuit 16 d is configured between the downstreamside of the solenoid coil 4 and the supply node of the boosting voltageVboost. The regeneration circuit 16 d includes a diode D4 and canregenerate excess power, accumulated in the solenoid coil 4, in thecharge capacitor 13 a when the MOSFETs_M2 to M4 are turned off.

The current detection unit 16 e includes a current detection resistor R2for detecting the current flowing from the solenoid coil 4 through thedownstream circuit 6 c and is configured by being connected in seriesbetween the source of the MOSFET_M4 and the ground. Although notillustrated, the current monitoring unit 15 c of the control IC 15 isconfigured using, for example, a comparison unit including comparator,an A/D converter, or the like and monitors, through the currentdetection unit 16 e, a current flowing through the solenoid coil 4 ofthe fuel injection valve 2.

The voltage monitoring unit 15 d of the control IC 15 is configuredusing an A/D converter (not illustrated), samples a terminal voltage onthe downstream side of the solenoid coil 4, and stores the sampling datainto the memory 15 e. The terminal voltage on the upstream side of thesolenoid coil 4 may also be sampled and stored into the memory 15 e.

When the energization control unit 15 b causes partial lift injection(minute injection) from the fuel injection valve 2, the energizationcontrol unit 15 b turns on MOSFETs_M4 of the cylinders #1 to #4 to beinjected and turns on MOSFETs_M2 to apply the boosting voltage Vboost tothe solenoid coil 4 of the fuel injection valve 2 and performsprocessing to close the valve element 5 by turning off MOSFETs_M2, M4before the lift of the valve element 5 ends completely.

When full lift injection (normal injection) is performed from the fuelinjection valve 2, the energization control unit 15 b turns onMOSFETs_M4 of the cylinders #1 to #4 to be injected through the drivecircuit 16 and turns on MOSFETs_M2 to apply the boosting voltage Vboostto the solenoid coil 4, and then turns off MOSFETs_M2 and turns on/offMOSFETs_M3 to apply the battery voltage VB and perform constant currentcontrol, and when an energization command time Ti has elapsed, theenergization control unit 15 b turns off MOSFETs_M3, M4 to stopenergization. Thus, at the time of full lift injection, after the liftof the valve element 5 ends completely, the processing of closing thevalve element 5 is performed.

When the drive circuit 16 interrupts the energization current afterenergizing the solenoid coil 4 on the basis of the energization controlof the energization control unit 15 b of the control IC 15, a flybackvoltage is generated in the solenoid coil 4. When the current of thesolenoid coil 4 is interrupted, the valve element 5 and the movable core7 are displaced in the valve-closing direction, so that an inducedelectromotive force based on the displacement of the valve element 5 andthe movable core 7 is generated in the solenoid coil 4. Therefore, theflyback voltage and the induced electromotive voltage are superposed onthe solenoid coil 4. The voltage monitoring unit 15 d stores a samplingresult, obtained by sampling the voltage generated in the solenoid coil4, into the memory 15 e.

As illustrated in FIG. 4, the microcomputer 14 has functions as aninjection amount change unit 14 d, a determination unit 14 e, aninjection amount calculation unit 14 f, a learning unit 14 g, and anarithmetic unit 14 h. In the drawings, the injection amount change unit14 d may be also referred to as INJECTION AMOUNT CAL, the determinationunit 14 e may be also referred to as DETERMINATION, the injection amountcalculation unit 14 f may be also referred to as INJECTION AMOUNT CAL,the learning unit 14 g may be also referred to as LEARNING, and thearithmetic unit 14 h may be also referred to as ARITHMETIC. Theinjection amount change unit 14 d has a function of increasing ordecreasing the required injection amount by increasing or decreasing theenergization command time Ti, for example. The injection amount changeunit 14 d desirably increases or decreases the required injection amountwithin a prescribed range in which it is determined that the travel andexhaust of the vehicle are not affected even when the required injectionamount is changed on the basis of the determination result of thedetermination unit 14 e. In particular, the microcomputer 14 desirablyincreases or decreases the required injection amount on the basis of thedetermination result of the determination unit 14 e.

The determination unit 14 e shows a function of determining the drivingstate of the vehicle. The driving state referred to here is, forexample, a driving state determined on the basis of the amount of intakeair detected by the intake air amount sensor 18 a. When the vehicle is apredetermined vehicle such as a hybrid vehicle, the driving stateindicates a mode state of an internal combustion engine traveling modein which the vehicle travels using the internal combustion engine, anelectric traveling mode in which the vehicle travels using an electricmotor, and the like.

The control IC 15 also has functions as an acquisition unit 15 f and avariation calculation unit 15 h. In the drawings, the acquisition unit15 f may be also referred to as Acquisition, and the variationcalculation unit 15 h may be also referred to as VARIATION CALCULATION.The acquisition unit 15 f of the control IC 15 has a function ofacquiring sample data of a voltage, generated when the fuel injectionvalve 2 is driven, which is used in calculation processing of adispersion value to be a degree of variation in the sampling data storedin the memory 15 e. The variation calculation unit 15 h calculates adispersion value to be the degree of variation from the sample data ofthe voltage acquired by the acquisition unit 15 f. The dispersion valueis output to the microcomputer 14.

The microcomputer 14 has a function of estimating a valve-opening timeand a valve-closing time (t2 to be described later) of the injectionhole 3 a based on the operation of the valve element 5. Themicrocomputer 14 repeats fuel injection control on the basis of therequired injection amount increased or decreased by the injection amountchange unit 14 d. The arithmetic unit 14 h obtains the valve-closingtime t2 for stopping the injection of fuel from the fuel injection valve2 on the basis of the dispersion value input from the control IC 15. Thelearning unit 14 g learns the valve-closing time t2. Further, it ispreferable that the injection amount calculation unit 14 f calculate themaximum injection amount and the minimum injection amount of therequired injection amount with which the valve-closing time t2 can bedetected, and the learning unit 14 g learn the valve-closing time t2 onthe basis of the maximum injection amount and the minimum injectionamount.

The control IC 15 has a function as a correction unit to receive theinjection command signal TQ and corrects the energization command timeTi, thereby correcting the energization command time Ti so as to matchan actual injection amount with a normal injection profile which is anideal injection amount.

An operation according to the present embodiment will be described.Normally, the microcomputer 14 executes tasks related to variousapplication programs in parallel, calculates the computing processingload of the microcomputer 14, and obtains parameters related to thestate of the internal combustion engine and a drive parameter fordriving the fuel injection valve 2 on the basis of the sensor signal Sof the sensor 18. For example, on the basis of the sensor signals S ofthe various sensors 18, the microcomputer 14 determines the warm stateof the internal combustion engine and determines whether the rotationalspeed of the internal combustion engine is higher than a predeterminedrotational speed.

The microcomputer 14 transmits these various kinds of information to thecontrol IC 15 together with an injection command signal TQ for singleinjection or multi-stage injection. Note that the informationtransmitted by the microcomputer 14 to the control IC 15 together withthe injection command signal TQ may be the sensor signal S of the sensor18 itself or may be a determination result determined on the basis ofthe sensor signal S of the sensor 18 or a signal representing anotherstate.

FIG. 5 illustrates a change in the terminal voltage on the downstreamside of the solenoid coil 4 detected by the voltage monitor unit 15 d inresponse to the turning off the MOSFETs_M2 to M4 after the microcomputer14 outputs the injection command signal TQ to the control IC 15 and theenergization command time Ti elapses. The voltage monitoring unit 15 dsamples the terminal voltage on the downstream side of the solenoid coil4 at a predetermined sampling interval during a predetermined period Taincluding at least timing t1 and timing t2 (see below) after theenergization end timing t0 and stores the sampling data of the voltageinto the memory 15 e.

When the energization current of the solenoid coil 4 is cut off afterthe lapse of the energization command time Ti, a flyback voltage isfirst generated in the solenoid coil 4. At this time, the terminalvoltage on the downstream side of the solenoid coil 4 rapidly rises andthen gradually drops to zero. The flyback voltage descends in a smoothcurve projecting downward on the basis of a time constant determined bythe circuit constants of the drive circuit 16 and the solenoid coil 4.

While the terminal voltage on the downstream side of the solenoid coil 4gradually decreases to zero, the movable core 7 starts moving in thedirection of closing the injection hole 3 a together with the valveelement 5 at timing t1 when a certain delay time has elapsed from theenergization end timing t0. The delay time is a time determined on thebasis of the internal structure of the fuel injection valve 2, that is,the relative positions of the fixed core 6 and the movable core 7, theweight of the movable core 7, the elastic forces of the first spring 8and the second spring 9, and the like.

When the valve element 5 and the movable core 7 start to move, aninduced electromotive force based on the movement of the valve element 5and the movable core 7 is generated in the solenoid coil 4, so that theterminal voltage on the downstream side of the solenoid coil 4 risesmore than the downward curve projecting downward as shown in timing t1to timing t2. At the valve-closing time t2 when the valve element 5closes the injection hole 3 a, the moving speed of the movable core 7becomes maximum, but since the valve element 5 is seated to close theinjection hole 3 a, the movable core 7 decelerates rapidly. At thistime, the induced electromotive force having been generated in thesolenoid coil 4 also changes rapidly, so that an inflection pointappears in the terminal voltage. Thereafter, the movable core 7 moves tothe injection hole 3 a side away from the locking portion 5 a of thevalve element 5, the induced electromotive voltage continues to begenerated until a timing after the valve-closing time t2, for example,t3.

As described above, the voltage monitor unit 15 d holds the samplingdata in the memory 15 e at a predetermined sampling interval for atleast a predetermined period Ta including the timings t1 to t2. Thus,the sampling data can be utilized for the analysis processing of thevalve-closing time t2.

For example, it is possible to calculate the inflection point of theterminal voltage of the solenoid coil 4 by differentiating the samplingdata by time. However, it has been found that, in a case where thisdifferentiation method is used, the smoothing effect of the samplingdata becomes greater when the sampling data is increased. Further, ithas been found that, due to the increase in the smoothing effect, a Qvalue of the amount of change in a differential value decreases, and asignal-to-noise ratio (S/N) deteriorates.

Therefore, as illustrated in FIG. 5, it is preferable to calculate thevalve-closing time t2 by calculating the dispersion value representingthe degree of variation in the sampling data that changes with time toobtain the inflection point of the terminal voltage on the downstreamside of the solenoid coil 4. It is preferable that the amount of changein the dispersion value of the sample data be calculated and that thetiming at which the amount of change is zero-crossed be specified as thevalve-closing time t2.

The amount of change in voltage caused by the change in the inducedelectromotive force is very small even in full lift injection. Inparticular, in the case of the partial lift injection, a change in themoving speed of the movable core 7 at the point in time of sittingbecomes small due to the small lift amount at the start of thevalve-closing operation, and the amount of change in the inducedelectromotive voltage becomes particularly small. When the inflectionpoint cannot be detected, the valve-closing time t2 cannot be detected,so that the valve-closing time t2 cannot be learned, and the requiredinjection amount cannot be corrected.

Therefore, it is preferable that the microcomputer 14 repeat the fuelinjection control on the basis of the required injection amount,increased or decreased by the injection amount change unit 14 d, andlearn the valve-closing time t2 by the learning unit 14 g. Inparticular, as illustrated in FIGS. 6 and 9, it is desirable that themicrocomputer 14 calculate the maximum injection amount and the minimuminjection amount of the required injection amount, with which thevalve-closing time t2 can be detected by the injection amountcalculation unit 14 f, and learn the valve-closing time t2 in the rangeof the maximum injection amount and the minimum injection amount.

A specific example will be described. For example, when the control IC15 detects the dispersion value each time one injection is made in S1and S2 of FIG. 6 and outputs the dispersion value to the microcomputer14, and the microcomputer 14 determines that the valve closing can bedetected in S3 of FIG. 6, the microcomputer 14 sets a valve-closingdetection possibility flag to Yes in S4, and changes the requiredinjection amount to slightly increase in S5.

As illustrated in FIG. 7, when the required injection amount is set tobe large, the valve-closing time t2 is delayed, and when the requiredinjection amount is set to be small, the valve-closing time t2 becomesearly. At this time, as shown by timing t0 to timing t8 in FIG. 7, whileit is determined that the valve closing can be detected, themicrocomputer 14 slightly increases the required injection amountstepwise by the injection amount change unit 14 d.

At timing t9 in FIG. 7, when the microcomputer 14 slightly increases therequired injection amount by the injection amount change unit 14 d, themicrocomputer 14 determines that the valve-closing detection isimpossible by acquiring an error value as the valve-closing detectionvalue in S3, sets the valve-closing detection possibility flag to No inS7, and slightly reduces the required injection amount in S8.

When detecting in S6 of FIG. 6 that the valve-closing detectionpossibility flag has changed from the previous value, that is, thevalve-closing detection possibility flag has changed from Yes to No, themicrocomputer 14 determines a maximum injection amount max in S9 anddetermines a slowest value tmax of the valve-closing time t2 in S10.Thus, by detecting the boundary which transitions from the valve-closingdetectable state to the valve-closing undetectable state at timing t9 inFIG. 7, the maximum injection amount max can be determined, and theslowest value tmax of the valve-closing time t2 can be determined

On the other hand, for example, when the control IC 15 detects thedispersion value each time the injection is made in S1 and S2 of FIG. 6,and the microcomputer 14 determines that the valve-closing detection isimpossible by acquiring an error value as the valve-closing detectionvalue in S3 of FIG. 6, the microcomputer 14 sets the valve-closingdetection possibility flag to No in S7 and slightly reduces the requiredinjection amount in S8. At this time, as shown by timing t10 to timingt18 in FIG. 8, while it is determined that the valve closing cannot bedetected, the microcomputer 14 slightly reduces the required injectionamount in a stepwise manner by the injection amount change unit 14 d.

When detecting in S6 of FIG. 6 that the valve-closing detectionpossibility flag has changed from the previous value, that is, thevalve-closing detection possibility flag has changed from No to Yes, themicrocomputer 14 determines the maximum injection amount max in S9 anddetermines the slowest value tmax of the valve-closing time t2 in S10.Thus, also by detecting the boundary which transitions from thevalve-closing undetectable state to the valve-closing detectable stateat timing t19 in FIG. 8, the maximum injection amount max can bedetermined, and the slowest value tmax of the valve-closing time t2 canbe determined

For example, conversely, when the control IC 15 detects the dispersionvalue each time one injection is made in S1 and S2 of FIG. 9, and themicrocomputer 14 determines that the valve closing can be detected in S3of FIG. 9, the microcomputer 14 sets a valve-closing detectionpossibility flag to Yes in S4, and changes the required injection amountto slightly decrease in S5 a.

When the microcomputer 14 continues to slightly reduce the requiredinjection amount by the injection amount change unit 14 d while thevalve-closing detection is possible, the microcomputer 14 eventuallyacquires an error value as the valve-closing detection value in S3.Then, the microcomputer 14 determines that the valve-closing detectionis impossible, sets the valve-closing detection possibility flag to NOin S7, and slightly increases the required injection amount in S8 a.

When detecting in S6 of FIG. 9 that the valve-closing detectionpossibility flag has changed from the previous value, that is, thevalve-closing detection possibility flag has changed from Yes to No, themicrocomputer 14 determines the minimum injection amount in S9 a anddetermines the fastest value of the valve-closing time t2 in S10 a.Thus, by detecting the boundary which transitions from the valve closingdetectable state to the valve closing undetectable state, the fastestvalue of the valve-closing time t2 can be determined while the minimuminjection amount is detected.

On the other hand, for example, when the control IC 15 detects thedispersion value each time the injection is made in S1 and S2 of FIG. 9,and the microcomputer 14 determines that the valve-closing detection isimpossible by acquiring an error value as the valve-closing detectionvalue in S3 of FIG. 9, the microcomputer 14 sets the valve-closingdetection possibility flag to No in S7 and slightly increases therequired injection amount in S8 a. While it is determined that thevalve-closing detection is impossible, the microcomputer 14 slightlyincreases the required injection amount in a stepwise manner by theinjection amount change unit 14 d.

When detecting in S6 of FIG. 9 that the valve-closing detectionpossibility flag has changed from the previous value, that is, thevalve-closing detection possibility flag has changed from No to Yes, themicrocomputer 14 determines the minimum injection amount in S9 a anddetermines the fastest value of the valve-closing time t2 in S10 a.Thus, also by detecting the transition boundary between the valveclosing detectable state and the valve closing undetectable state, thefastest value of the valve-closing time t2 can be determined while theminimum injection amount is detected.

Thereafter, the microcomputer 14 outputs the injection command signal TQto the control IC 15 so as to increase or decrease the requiredinjection amount by the injection amount change unit 14 d within therange of the obtained maximum injection amount and minimum injectionamount and learns the valve-closing time t2 on the basis of thedispersion value calculated by the control IC 15 for each of theseinjections. As a result, the valve-closing time t2 can be learned withhigh reliability.

By storing the detected valve-closing time t2 into the memory 14 b, themicrocomputer 14 can learn the relationship between the requiredinjection amount within the range of the maximum injection amount andthe minimum injection amount and the detection result of thevalve-closing time t2. The valve-closing time t2 according to a standardproduct is predetermined, so that the microcomputer 14 can compare thestandard value with the detected valve-closing time t2 to learn thedeviation. The microcomputer 14 can correct the required injectionamount by using the learned value to realize injection accuracysatisfying the emission requirement.

The microcomputer 14 desirably increases or decreases the requiredinjection amount within a prescribed range in which it is determinedthat the travel and exhaust of the vehicle are not affected even whenthe required injection amount is changed on the basis of thedetermination result of the determination unit 14 e that determines thedriving state of the vehicle by the function of the injection amountchange unit 14 d. The driving state of the vehicle determined by thedetermination unit 14 e is the driving states of various vehiclesdetermined on the basis of the sensor signals S of the sensors 18 andindicates, for example, an amount of intake air detected by the intakeair amount sensor 18 a, an A/F value detected by the A/F sensor 18 b, adriving mode in the case of a predetermined vehicle such as a hybridvehicle, that is, an internal combustion engine traveling mode in whichthe vehicle is traveling using the internal combustion engine, anelectric traveling mode in which the vehicle travels using an electricmotor, and the like.

In this case, it is desirable to learn the valve-closing time t2 on thecondition that the amount of intake air detected by the intake airamount sensor 18 a is greater than a predetermined value. This isbecause when the amount of intake air is greater than the predeterminedamount, there is little possibility of affecting the traveling state.When the vehicle is a predetermined vehicle such as a hybrid vehiclehaving an internal combustion engine traveling mode in which the vehicletravels using an internal combustion engine and an electric travelingmode in which the vehicle travels using an electric motor, it isdesirable to learn the valve-closing time t2 in the electric travelingmode. This is because the traveling control of the electronic controlunit 1 is not affected in the electric traveling mode.

In addition, when the present disclosure is applied to a multi-stageinjection in which other injections are continuously performed before orafter the main injection, it is desirable to learn the valve-closingtime t2 by increasing or decreasing the required injection amount of oneor more injections determined to have no effect on the traveling andexhaust of the vehicle, among the multi-stage injections. When it isdetermined that the injection control function has no effect on thetraveling control or the exhaust, the learning function may be activatedat any timing.

As described above, according to the present embodiment, themicrocomputer 14 repeats the fuel injection control on the basis of therequired injection amount increased or decreased by the injection amountchange unit 14 d, so that the valve-closing time t2 determined on thebasis of the dispersion value is learned by the learning unit 14 g. As aresult, the valve-closing time t2 can be learned with high reliability.In particular, it is preferable that the microcomputer 14 calculate themaximum injection amount and the minimum injection amount of therequired injection amount, with which the valve-closing time t2 can bedetected by the injection amount calculation unit 14 f, and learn thevalve-closing time t2 in the range of the maximum injection amount andthe minimum injection amount.

Other Embodiments

The present disclosure is not limited to the embodiment described abovebut can be implemented in various variations and can be applied tovarious embodiments without departing from the gist thereof. Forexample, the following modifications or extensions are possible.

The embodiment has been described in which the microcomputer 14 isprovided with the functions as the injection amount change unit 14 d,the determination unit 14 e, the injection amount calculation unit 14 f,the learning unit 14 g, and the arithmetic unit 14 h, and the control IC15 is provided with the functions as the acquisition unit 15 f and thevariation calculation unit 15 h. However, these functions may beprovided in either the microcomputer 14 or the control IC.

Although it has been that the microcomputer 14 and the control IC 15 areconfigured using separate integrated circuits, the microcomputer 14 andthe control IC 15 may be configured integrally. In the case of theintegrated configuration, it is preferable to use a high-speedprocessing device for the configuration.

In the embodiment described above, the present disclosure has beenapplied to in-cylinder injection in which the injection is directly madeinto the combustion chamber of the internal combustion engine. However,the present disclosure is not limited thereto and may be applied to portinjection in which fuel is injected in front of an intake valve. Thepresent embodiment is not limited to the in-cylinder injection in whichthe injection is directly made into the combustion chamber of theinternal combustion engine. It has been described in aneasy-to-understanding manner that the body 3 of the fuel injection valve2 is configured using one member, but the present disclosure is notlimited thereto.

In the embodiment described above, the form has been shown in which theterminal voltage on the downstream side of the solenoid coil 4 isacquired in order to detect the valve-closing time t2, but the voltagenode to be acquired is not limited to the downstream side of thesolenoid coil 4. The circuit configuration of the drive circuit 16 isnot limited to the configuration described above. The form in which thecalculation is made using the dispersion value as the degree ofvariation has been shown, but the present disclosure is not limited tothis. The degree of variation may be changed so as to obtain the squareof an expected value, or the degree of variation may be calculated byacquiring an absolute value of a value obtained by subtracting anaverage value from the sample data, adding all these values, and thenperforming the square. Thus, the number of times of multiplication canbe reduced, and the arithmetic processing load can be reduced.

The method using the microcomputer 14 and the control IC 15 according tothe present disclosure may be achieved by a dedicated computer includinga processor and a memory programmed to execute one or more functionsembodied by a computer program. Alternatively, the control device andthe method according to the present disclosure may be achieved by adedicated computer including a processor with one or more dedicatedhardware logic circuits. Alternatively, the control method and themethod according to the present disclosure may be achieved using one ormore dedicated computers including a combination of the processor andthe memory programmed to execute one or more functions and the processorwith one or more hardware logic circuits. The computer program may bestored in a computer-readable non-transitory tangible storage medium asan instruction to be executed by the computer.

The numerals in parentheses in the claims indicate correspondence withthe specific means according to the embodiment described above as oneaspect of the present disclosure and do not limit the technical scope ofthe present disclosure. An aspect in which a part of the embodimentdescribed above is omitted so far as the difficulty can be solved canalso be regarded as an embodiment. Any aspects conceivable within thenature of the invention specified by wordings described in claims canalso be regarded as embodiments.

Although the present disclosure has been described in accordance withthe above embodiment, it is understood that the present disclosure isnot limited to the embodiment or structure. The present disclosure alsoencompasses various modified examples and modifications within a uniformrange. In addition, various combinations and forms, as well as othercombinations and forms including only one element, more than that, orless than that, are also within the scope and idea of the presentdisclosure.

Here, the process of the flowchart or the flowchart described in thisapplication includes a plurality of sections (or steps), and eachsection is expressed as, for example, S1. Further, each section may bedivided into several subsections, while several sections may be combinedinto one section. Furthermore, each section thus configured may bereferred to as a device, module, or means.

1. An injection control device for controlling injection of the fuel toan internal combustion engine by driving a fuel injection valve to causea vehicle to travel, the injection control device comprising: anarithmetic unit configured to obtain a valve-closing time for stoppingthe injection of the fuel from the fuel injection valve based on adegree of variation in a time change of a voltage generated when thefuel injection valve is driven based on a required injection amount; aninjection amount change unit configured to increase or decrease therequired injection amount; and a learning unit configured to repeatinjection control of the fuel based on the required injection amountthat is increased or decreased by the injection amount change unit, tolearn the valve-closing time obtained by the arithmetic unit.
 2. Theinjection control device according to claim 1, further comprising: aninjection amount calculation unit configured to calculate a maximuminjection amount and a minimum injection amount of the requiredinjection amount with which the valve-closing time is detectable,wherein: the learning unit is configured to learn the valve-closing timeby the injection amount change unit increasing or decreasing therequired injection amount within a range between the maximum injectionamount and the minimum injection amount.
 3. The injection control deviceaccording to claim 1, further comprising: a determination unitconfigured to determine a driving state of the vehicle, wherein: theinjection amount change unit is configured to increase or decrease therequired injection amount within a prescribed range in which it isdetermined that traveling and exhaust of the vehicle are not affectedeven when the required injection amount is changed based on adetermination result of the determination unit.
 4. The injection controldevice according to claim 1, wherein: on a condition that an intakeamount of air sucked into the internal combustion engine is greater thana predetermined amount, the injection amount change unit increases ordecreases the required injection amount and the learning unit learns thevalve-closing time.
 5. The injection control device according to claim1, wherein: the vehicle is a predetermined vehicle having an internalcombustion engine traveling mode in which the vehicle travels using theinternal combustion engine and an electric traveling mode in which thevehicle travels using an electric motor; and on a condition that thevehicle is in the electric traveling mode, the injection amount changeunit increases or decreases the required injection amount and thelearning unit learns the valve-closing time.
 6. The injection controldevice according to claim 1, wherein: the injection amount change unitis configured to increase or decrease the injection amount for a part ofmulti-stage injection.
 7. An injection control device for controllinginjection of the fuel to an internal combustion engine by driving a fuelinjection valve to cause a vehicle to travel, the injection controldevice comprising: one or more processors; and a memory coupled to theone or more processors and storing program instructions that whenexecuted by the one or more processors cause the one or more processorsto at least: obtain a valve-closing time for stopping the injection ofthe fuel from the fuel injection valve based on a degree of variation ina time change of a voltage generated when the fuel injection valve isdriven based on a required injection amount; increase or decrease therequired injection amount; and repeat injection control of the fuelbased on the required injection amount that is increased or decreased tolearn the valve-closing time that is obtained.